﻿39 
  

  

  Lacaze-Dutluer''s 
  observations, 
  published 
  more 
  than 
  twent}' 
  

   years 
  ago 
  (Ann. 
  d. 
  Sc. 
  Nat. 
  1854. 
  Organes 
  genitaux 
  des 
  

   Acephales 
  Lamellibranches.; 
  and, 
  Comptes 
  rcndiis, 
  1855, 
  x 
  4, 
  

   415-420. 
  Des 
  organes 
  de 
  la 
  generation 
  de 
  I'huitre), 
  are 
  very- 
  

   similar 
  to 
  those 
  of 
  Mobius. 
  He 
  says 
  that 
  at 
  any 
  given 
  time 
  

   each 
  oyster 
  is 
  almost 
  exclusively 
  male 
  or 
  almost 
  exclusively 
  

   female, 
  and 
  he 
  thinks 
  that 
  the 
  young 
  oysters 
  are 
  functionally 
  

   male, 
  and 
  become 
  female 
  as 
  they 
  grow 
  older. 
  

  

  As 
  I 
  have 
  already 
  stated, 
  I 
  have 
  found 
  oysters 
  only 
  one 
  

   year 
  old 
  which 
  contained 
  ripe 
  eggs, 
  and 
  eggs 
  only, 
  and 
  others 
  

   of 
  the 
  same 
  age 
  which 
  were 
  exclusively 
  male, 
  and 
  I 
  have 
  suc- 
  

   ceeded 
  in 
  fertilizing 
  the 
  eggs 
  of 
  the 
  one 
  with 
  the 
  fluid 
  of 
  the 
  

   other. 
  This 
  observation, 
  which 
  is 
  corroborated 
  by 
  Gerbe's 
  

   statement 
  (Zool. 
  Record, 
  1876, 
  xiii., 
  Mol. 
  p. 
  62), 
  that 
  among 
  

   435 
  European 
  oysters 
  one 
  year 
  old, 
  he 
  found 
  35 
  with 
  young; 
  

   127 
  with 
  ripe 
  eggs, 
  and 
  189 
  with 
  ripe 
  semen, 
  seems 
  to 
  be 
  

   sufficient 
  to 
  show 
  the 
  incorrectness 
  of 
  Lacaze-Duthier's 
  con- 
  

   jecture 
  that 
  the 
  functionally 
  male 
  condition 
  precedes 
  the 
  func 
  

   tionally 
  female 
  condition. 
  

  

  MANNER 
  OF 
  FERTILIZATION. 
  

  

  Although 
  the 
  American 
  oyster 
  seems 
  well 
  adapted, 
  like 
  the 
  

   European 
  species, 
  and 
  various 
  other 
  marine 
  and 
  fresh- 
  water 
  

   Lamellibranchs, 
  to 
  draw 
  into 
  its 
  mantle-chamber, 
  with 
  the 
  sea- 
  

   water, 
  the 
  spermatozoa 
  discharged 
  from 
  the 
  mantle-chambers 
  

   of 
  neighboring 
  oysters, 
  and 
  thus 
  to 
  bring 
  about 
  the 
  fertiliza- 
  

   tion 
  of 
  the 
  eggs 
  inside 
  the 
  cavity 
  of 
  the 
  shell, 
  this 
  does 
  not 
  

   seem 
  to 
  occur. 
  

  

  I 
  have 
  carefully 
  searched 
  the 
  gills 
  and 
  mantles 
  of 
  more 
  than 
  

   a 
  thousand 
  oysters 
  at 
  a 
  time 
  when 
  the 
  reproductive 
  organs 
  

   were 
  plainly 
  seen 
  to 
  be 
  discharging 
  their 
  ripe 
  contents, 
  and 
  

   have 
  not 
  found 
  a 
  single 
  fertilized 
  eg;g 
  or 
  embryo 
  in 
  any 
  part 
  

   of 
  the 
  mantle-chamber, 
  in 
  or 
  on 
  the 
  gills, 
  or 
  anywhere 
  else 
  

   inside 
  the 
  shell. 
  This 
  negative 
  evidence, 
  together 
  with 
  the 
  

   fact 
  that 
  the 
  eggs 
  can 
  be 
  hatched 
  after 
  they 
  have 
  been 
  arti- 
  

   ficially 
  removed 
  from 
  the 
  ovaries 
  seems 
  sufficient 
  to 
  prove, 
  in 
  

   the 
  absence 
  of 
  all 
  evidence 
  to 
  the 
  contrary, 
  that 
  the 
  eggs 
  of 
  

   the 
  American 
  oyster 
  undergo 
  development 
  in 
  the 
  open 
  ocean. 
  

  

  